With gradual improvement of the electric vehicle technology and the power battery technology, the market has an increasing requires on the power battery module in energy density, power, cycle life, safety, etc. Developing a heat management unit and a heat management assembly satisfying the requirement of existing power battery module system becomes an essential project in development process of power battery system.
Regarding the battery management system, temperature and temperature consistency are basic indexes of assessing performance, life and safety of the power battery system, and also are important parameters of estimating state of charge (SOC) and control policy of the battery management system. However, the working temperature range of the vehicle is from −30° C. to 80° C. and is far beyond the working temperature range of the power battery. Taking a specific type of a lithium-ion power battery for example, an optimal working temperature of the lithium-ion power battery ranges from 20° C. to 40° C. If the battery works at a temperature higher than 40° C. for a long time, the cycle life will be greatly reduced, and meanwhile the thermal runaway of the lithium-ion power battery will be caused at the high temperature; if the lithium-ion power battery works at a temperature lower than 0° C., besides potential security hazard possibly caused by charging at a low temperature, the lower output power and functional degradation cannot satisfy the demands of the normal working of the vehicle.
Therefore, the power battery system generally uses a heat management assembly and a thermal management module provided outside the batteries to heat and cool the batteries so as to rapidly adjust the temperature of the battery module to an appropriate working temperature range.
At present, the popular solutions of electric vehicle at domestic and oversea use an air blower system or a water cooling system to achieve the target for heat management of the battery module. Besides the air blower system is difficult to satisfy the requirements of waterproof level and dustproof level, the heat exchange efficiency of the air blower system is also lower, it is difficult to achieve the target of the temperature consistency of 5° C. required by the general lithium-ion battery, especially for the large lithium-ion battery pack. Although most of the battery packs using the water cooling system solution specially design a battery cooling plate at present, they are generally limited due to small size, heavy weight and higher manufacturing cost, and the solution using the foam and the thermal conductive pad to improve thermal transfer between the cooling plate and the battery module cannot resolve the life problem caused by the long term aging. In addition, the additional pipeline connections between the cooling plates in the battery pack not only occupy more design space and increase cost, but also bring security problem caused by leakage. In the cold winter, the function of heating rapidly at low temperature is more important. At present, most of the heating solutions of the battery pack have disadvantages such as low heating efficiency, uneven heating, bad reliability of the heating units and the like, and most of the heating solutions select to integrate the heating units in the battery module or separate the heating units from the cooling plate units, which also exist the problems of inconvenient maintenance and difficult installation and so on.